Electrically operated sidereal clock



Dec. l0, 1940. G. R. McDoNALD 2,224,268

ELECTRICALLY OPERA'IVED SIDEREAL CLOCK Filed March 9, 1958 2She'ets-Sheet l 46 5 47 mila' "WWMN,

zz zo 1923 f@ i E' I; INVENTOR.

ATTORNEYS.

G. R. MCDONALD 2,224,268 ELECTRICALLY OPERATED'SIDEREAL CLOCK De. 1o,1940.

Filed March 9, 1958 2 Sheets-Sheet 2 N 72W, mf@

TTOBNEYS' Patented Dec. 10, 1940 UNITED STATES PATENT OFFICEELECTRICALLY OPERATED SIDEREAL CLOCK My invention relates toimprovements in an electrically operated sidereal clock, and itconsis-ts of the combinations, constructions and arrangementshereinafter described and claimed.

5 An object of my invention is to provide an electrically operatedsidereal clock which is an improvement over my invention on a Manual orautomatic means for correcting timekeeping mechanisms, patented January5, 1937, No. 2,06,357. In the patented device, I show translation gearsplaced between a synchronous motor and a clock mechanism for causing theclock mechanism to keep sidereal time with a yearly error of 57.28seconds. I further show in the patent, a correcting mechanism operatedby the clock mechanism for continuously correcting the sidereal time: sothat an error of only one-half a second in a year result instead of57.28 seconds.

I am well aware that clocks have been made which show both mean solarand the corresponding sidereal time operated by a common prime mover.The prime mover may be regulated to keep either mean solar or siderealtime, and the other ferm of time corresponding to that to which theprime mover is regulated, is derived by a connecting gear train designedto give as nearly as possible the ratio 1.00273791 which closelyrepresents the ratio given by the length of the solar day divided by thelength of the sidereal day (Scientiiic American, December, 1937, page361) These clocks depend upon direct gear trains which require gearshaving a large number of teeth and therefore of a size that will be toolarge for standard sized clocks.

In the present invention, both sidereal and solar clock mechanisms areoperated by a prime mover. A planetary gear train is provided in thesidereal clock mechanism, and the sun gearof this train is directlyconnected to the solar clock mechanism by a train of gears which willgive a ratio suiiiciently close to the ratio 1.00273791, that in oneyear, the indication shown by the sidereal time indicating hands, lags.024 second behind the indication which would be shown if the gear ratiobetween the two clock mechanisms were exact. The gears used in theplanetary train and in the train connecting the sun gear with the solarclock, are of the size usually used in clock mechanisms. The siderealsweep second hand should have 394258933 revolutions added to it daily.This value is based. on the value of the sidereal difiere-nce per day asstated in the December, 1937, Soient-inc American, page 361; namely,three minutes and 56.55536 seconds. I have found a 55 gear ratio thatwill add 3.9425825235 revolutions a day to the clock mechanism givingsidereal time and therefore correct sidereal time will result with theexception of the slight error of .024 second which the clock will runslow in a year.

Other objects and advantages will appear in the following specification,and the novel features of the device will be particularly pointed out inthe appended claims.

My invention is illustrated in the accompanying drawing forming a partof this application, in which Figure l is a front elevation of thedevice;

Figure 2 is a schematic view of the gear mechanisms in both the solarand sidereal clocks showing the gears twice their normal size forclarity; and Figure 3 is a section along the line 3 3 of Figure 2 andshows the gear in natural size and correctly positioned in the clockcasing.

In carrying out my invention, I provide a clock casing indicatedgenerally at I and this casing has a face Z. Both the solar time andsidereal time are indicated on the face 2. The face 2 is provided with acircular depression 3 in which a dial 4 is marked for indicating solartime. Numbers 5 are placed adjacent to the markings on the dial 4 andindicate the solar hours from one to twelve in the usual manner. A solarminute hand 6 and a solar hour hand 'I are movable over the dial 4 inthe usual manner for indicating n The mechanism for operating the solartime. solar hands 6 and l will be described hereinafter. The face 2 ofthe clock has numbers one to twenty-four printed thereon and indicatedat 8 for showing sidereal time. The sidereal sweep second hand is shownat 9, the sidereal minute hand is shown at II) and the sidereal hourhand is shown at III. All of these hands are moved by a mechanismhereinafter described. The hands 9, I0 and II will pass over the hands Eand I of the solar clock because the depression 3 receives the hands 6and I. In addition to the numbers 8, I provide markings I2 to indicatesidereal minutes and every iiith marking is numbered from five to sixtyinclusive, to indicate sidereal minutes or seconds. The numbers fromiive to sixty inclusive, are shown at I3.

It is possible to manually adjust the solar hands 6 and l by means of aknob I4 that is connected to the hands in a manner presently to bedescribed. In like manner, a knob l5 may be adjusted for moving thesidereal sweep second hand 9, and a knob I6 may be manually adjusted formoving the sidereal minute and hour hands Il! and II. All of thesemanual corrections may be.

made without interfering with the proper functioning of the clockmechanisms.

In Figure 2 I show how the solar and sidereal clock hands are operatedfrom a single synchronous motor indicated generally at I1. This motormaybe of the self-starting type, if desired, and will operate from asource of alternating current which is regulated or controlled toprovide a reliable source of solar time. It is possible to use aspring-wound motor as a source of power rather than the electric motorI1, if desired, as the improvement in the art is to oiTer a convenient,method of obtaining sidereal time where the v'revolution for each minuteof mean solar time.

prime mover is regulated in indicate solar time;

The motor I 1 rotates a gear I8 and the gear I9v meshes with a gear I9having one hundred teeth. The gears in Figure 2 are shown twice theirnatural size for clarity. The gear I9 carries a pinion 26 with ten teethand the pinion meshes with a gear 2| that has forty-five teeth. The gear2| carries a pinion -22 with twelve teeth and the pinion meshes with alarge gear 23 having fortyeight teeth. The gear 23 hasan integral gear24 that has eighteen teeth thereon andv this gear rotates at three andone third revolutions perminute, solar time.vr It is this gear 24 thatis operatively connected to thesolar timekeeping mechanism, and also tothe sidereal timekeepingmechanism. I will first describe the solartimekeeping mechanism.

A large gear 25 having sixty teeth meshes with the gear 24 and this gearis rotatably mounted on Va shaft Ak26 that carries the solar minute hand6. `Thegear 25 carries a pinion 21 having nine teeth and this pinionmeshes with a large gear 28' having sixty teeth. The large gear 28 alsocarries a Vpinion 29 that has seven teeth thereon and the pinion 29meshes with a large gear 3U having sixty-three teeth thereon.

It will be noted from Figure 2 that the gear 38 isrigidly connected to alarge gear 3| by means of a hub 32. The hub 32 frictionally engages witha sleeve 33 and this sleeve is rigidly secured to the shaft 26. Arotation of the gear 30 will cause the shaft 26 to rotate and thus movethe minute hand 6, but it is possible to manuallyy rotate the shaft 26when it is desired to correct the time indicated by the solar hands 6and 1. The sleeve 33 has a gear 34 connected thereto and a pinion 35 maybe moved into mesh with the gear 34 when it is desired to correct thesolar time. rlhe pinion 35 is carried by a shaft 36 on which the knob|4is mounted. Before the knob I4 is rotatedV for correcting the solartime, it is manually moved inwardly against a spring, not shown, to meshthe pinion 35 with the gear 34. The pinion 35 will be automaticallydisconnected from the gear 34 when the knob I4 is released.

The shaft 26 has a gear 31 that is rigidly connected thereto and thegear has twelve teeth. The gear meshes with a large gear 38 providedwith forty-eight teeth. A gear 39 with fifteen teeth is rigidly securedto the gear 38 and meshes with a large gear 40 which has forty-fiveteeth. The gear 4U is rotatably mounted on the shaft 26 and carries asleeve 4| that in turn has the hour hand 'I connected therewith. Thegear train-31, 38, 39 and 40 has a ratio of one to twelve in order thatthe minute hand 6 will make twelve revolutions to one revolution of thehour hand 1.

I will now explain the-mechanism for actuating the sidereal hands 9, I0and I I. A gear 42 meshes with the gear 24 and has forty-eight teeth.The gear 42 is rotatably mounted upon a shaft 43 and thegear will rotateone and one fourth revolu-v hand-9 would indicate solar time.

tions per minute solar time. A pinion 44 is rigidly connected to thegear .42 and carries sixteen teeth. A large gear 45 having sixty teethis concentrically mounted with respect to the shaft 43. The gear 45carries a stud 41 that in turn rotatably carries two planetary gears 48and 49 that are rigidly connected together by a hub 41'. The gear 48 hastwenty teeth and meshes with the gear 44, While the gear 49 has eighteenteeth and meshes witha gear 50 that has `eighteen teeth and is keyed tothe spindle or shaft 43.

The number of teeth chosen for the gear or pinion 44 will cause thespindle 43 to make one The prime mover or motor I1 will rotate thepinion 44, one and one fourth revolutions per minute, solar time, andthe gear 50 will rotate the spindle 43, one revolution per minute, solartime. The sidereal sweep second hand 9 is mounted on the spindle 43.Should the gear 45, therefore, be heldagainst rotation, the siderealsweep second Before describing how the gear 45 is rotated in order tocause the sweep second hand 9 to indicate sidereal time instead of solartime, it is best to describethe gear trains that operate the siderealhand I0, and the sidereal hour hand II.

A pinion 5I has nine teeth and is mounted on the 'spindle 43 by softfriction s0l that it may slip ron the shaft 43 during the setting of thehands I0 andYV II by the knob I6. This pinion meshes with a large gear52 that has sixty teeth. A pinion 53 having seven teeth is rigidlyconnected to Vthegear 52 and meshes with a large gear 54 that hassixty-three teeth. The gear 54 is keyed to a sleeve 55 that in turncarries the sidereal minute hand I0. The sleeve has a gear 56 rigidlyusecured thereto and a pinion 51 may be manually moved into engagementwith the gear 56 for rotating the sleeve 55 and setting the minute handI9. `The pinion 51 is mounted on a shaft 58 that carries the knob I6.

A pinion 59 is keyed to the sleeve 55 and has fourteen teeth. Thispinion meshes with a large gear 60 that has fifty-six teeth, and thislarge gear in turn carries a pinion 6| that has ten teeth. The pinion 6|meshes with a large gear 62. provided with sixty teeth. The gear 62carries a sleeve 63 that is rotatably mounted on the sleeve 55. Thesleeve 63 carries the sidereal hour handv Il'. The ratio of the geartrain 5|, 52, 53 and 54 is one to sixty, while the ratio of the geartrain 59,60, 6| and 62 is one to twenty-four. This will cause thesidereal sweep second hand 9 to make sixty revolutions for onerevolution of the sidereal minute hand I0, and will cause the siderealminute hand Il! to make twenty-four revolutions for one revoltuion ofthe sidereal hour hand Il.

I will now describe how the gear 45 is rotated for" adding to thesidereal clock .mechanism 3.9425558235 minutes per day. The gear 45 isconnected to the gear 3| by two gears 64 and 65 that arefrictionallyvconnected together. The gears .64 and are not shown intheir full size in the diagrammaticshowing of Figure 2, but are shown inFigure 1 by dotted lines and also in Figure 3. The gear 64 is rigidlyconnected to a hub 66, while the gear 65 is frictionally secured to thehub." The gear 64 has seventy-one teeth and the gear 65 has eighty-fiveteeth. Since the gear 3| has `fifty-nine teeth' and rotates twenty-fourtimesyin one solar day, the gear 45 will be rotated 19.712941176revolutions in the same period of time in a clockwise direction. Sincethe planetary ratio of the train of gears 44, 48, 49 and 50 is four tove, it requires iive revolutions of the gear 45 to impart one additionalrevolution to the sidereal sweep second hand 9 over that alreadyimparted to it by the gear train 44-50. In other words, if the gear 44were held stationary and the gear 4t is retained in mesh with the gear44, one revolution of gear 45 clockwise, would cause only one-fifth of arevolution of the sidereal sweep second hand clockwise. As alreadystated the gear 45 is caused to make 19.7129411'76 revolutions in aclockwise `direction in twenty-four hours, solar time, therefore thesidereal sweep second hand 9 will make one-iifth of 19.7129411'76revolutions or 3.9425882155 revolutions every twenty-four hours solartime, over and in addition to the number of revolutions imparted to itby the gear train 44-50 every twenty-four hours solar time. rlhisrepresents the adding in of sufficient sidereal time units over thenumber of solar time units to equal the sidereal time. This is a veryclose approximation of sidereal time because in a year of running thesidereal clock will only be .O24 second slow with respect to what theactual sidereal time would be corresponding to the time indicated by thesolar time indicating hands. It is possible to manually set the siderealsweep second hand 9 in the following manner: The hub 65 has a gear 51rigidly secured thereto and a pinion S8 may be moved into mesh with thegear El for rotating it. The gear 68 is mounted on a shaft 69 and theknob I5 is manually rotated for rotating the gear 6l. The turning of theknob I5 will rotate the gear 64 and the gear 45. The gear 45 inrotating, will carry with it the planetary gears 48 and 49 and the gear49 will rotate the gear 50 and shaft 43 for moving the sidereal sweepsecond hand 9 in the desired direction.

The clock face, as already stated, shows at once both solar time andsidereal time that corresponds therewith. The sidereal clock hands arecaused to move at a faster rate than the solar clock hands by amechanism deriving its power from the solar clock mechanism. The gearschosen for operating the sidereal clock mechanism at a faster rate thanthe solar clock mechanism are small in size so as to readily fit into astandard clock casing. It would be possible to add a sweep second handto the solar dial 4 by the addition of suitable gearing, withoutaffecting the gear train that causes the sidereal clock to move fasterthan the solar clock.

There are 365.2421 solar days in a year and 366.2421 sidereal days inthe same year. The ratio of solar days to sidereal days is 1.00273791.Each solar day, 3.94258933 minutes must be added into the siderealclock. In other words, each day the sidereal minute hand must traverse3.94258933 more of those divisions marked from one to sixty on the dialthan does the solar minute hand. The gears 3l, 65, 64, 45, 49 and 50,add in 3.942588235 minutes a day to the shaft 43, and this increment isa Very close approximation of sidereal time, the loss in a yearamounting to .024 of a second. It is to be understood that wherever thewords solar time are used, means solar or mean time is meant.

While I have shown only the preferred form of my invention, it should beunderstood that various changes or modications may be made within thescope of the appended claims without departing from the spirit of theinvention.

I claim:

l. In combination, a gear, means for rotating the gear in direct ratioto a unit of solar time, a solar time-keeping clock actuated by thegear, a second timekeeping clock actuated by the gear and including aplanetary gear train, and gear connections between the solar clock andthe planetary gear train for adding in suflicient revolutions forcausing the second clock to keep sidereal time.

2. In combination, a solar clock mechanism, a second clock mechanism,common means for operating both mechanisms and for causing the solarclock to keep mean solar time, said second clock mechanism including aplanetary gear train, and a train of gears connecting the solar clockwith the planetary gear train for causing the second clock mechanism tokeep sidereal time.

3. In combination, two sets of time indicating means, common means foractuating both sets of time indicating means, said common means beingregulated to give mean solar time, means operatively connected to one ofsaid sets of time indio eating means for continually causing the othertime indicating means to function at a higher rate of speed and indicatesidereal time, said last named means including a planetary gear train.

4. In` combination, two sets of time indicating means, a common primemover for operating both of said sets of time indicating means, meansinterconnecting said sets of time indicating means for providing adefinite ratio between the time indicating means, said interconnectingmeans including a planetary gear train.

5. In combination, two clock mechanisms common means for operating bothmechanisms and regulated to keep mean solar time, means interconnectingthe two clock mechanisms for causing one of them to keep sidereal time,said last named means including a planetary gear train.

6. In combination, a solar clock mechanism, a second clock mechanism,common means for operating both clock mechanisms and causing the solarclock to keep mean solar time, a gear included in the solar clockmechanism and rotated by the mechanism, a second gear in the secondclock mechanism and rotating independently thereof, a gear traininterconnecting the first and second gears for causing the second gearto rotate at a predetermined speed, a planetary gear train including twosun and two planetary gears, the planetary gears being connectedtogether and rotating in unison on a shaft carried by the second gear,the two sun gears connecting the planetary gears with the commonoperating means and with the second clock mechanism, whereby the iirstand second gears, and the interconnecting gear train will cooperate withthe planetary gear train for causing the second clock mechanism to keepsidereal time.

GEORGE R. MCDONALD.

